Measuring the Frequency-dependency of the Critical Field of Carrier Multiplication in GaAs

For several years, the clock speed of silicon-based computer processors (and other electronics) has plateaued at single-digit gigahertz frequencies, leaving room for other materials to be explored as replacements and improvements. Diodes and transistors function due to field-induced carrier multiplication in the semiconductor material, and silicon devices appear to have reached their speed limit. Material properties, such as the critical field for carrier multiplication, are frequency dependent. Testing the possibility of improvement in diode switching times using light in the terahertz (THz) frequency range can offer a solution. Intense THz radiation can be used to excite carriers in semiconductors, testing if the switching times can be orders of magnitude faster. Currently, the electric fields we generate are not strong enough to excite carriers into the conduction band, so we use arrays of micron sized meta-structures deposited on the surface, locally enhancing the THz electromagnetic radiation, making the field strong enough to excite electrons in GaAs. Our goal is to help develop materials and understand properties central to realizing high-speed electronics. Here we show THz frequency-dependent measurements of the critical field of carrier multiplication in GaAs.